• Journal of Astronomy and Space Sciences
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• v.19 no.2
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• pp.151-162
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• 2002

Two approximate calculation models for a cosmic radiation shielding in satellite are compared with detailed 3-dimensional calculation results. One is a sectoring method and the other is a chord-length distribution method. Shielding caltulation is performed for KITSAT-1 under the assumed environment at SAA (South Atlantic Anomaly) location with AP-8 radiation spectrum model. When both approximate models are applied, calculation error is expected compared with 3-D detailed geometry calculation because of straight knock-on assumption neglecting the deflection of incident proton. However, both approximate models showed good agreements with 3-dimensional detailed Monte Carlo calculation in two dose detector locations.

• Journal of Astronomy and Space Sciences
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• v.33 no.2
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• pp.75-92
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• 2016

It is generally believed that the high energy emissions from isolated pulsars are emitted from relativistic electrons/positrons accelerated in outer magnetospheric accelerators (outergaps) via a curvature radiation mechanism, which has a simple exponential cut-off spectrum. However, many gamma-ray pulsars detected by the Fermi LAT (Large Area Telescope) cannot be fitted by simple exponential cut-off spectrum, and instead a sub-exponential is more appropriate. It is proposed that the realistic outergaps are non-stationary, and that the observed spectrum is a superposition of different stationary states that are controlled by the currents injected from the inner and outer boundaries. The Vela and Geminga pulsars have the largest fluxes among all targets observed, which allows us to carry out very detailed phase-resolved spectral analysis. We have divided the Vela and Geminga pulsars into 19 (the off pulse of Vela was not included) and 33 phase bins, respectively. We find that most phase resolved spectra still cannot be fitted by a simple exponential spectrum: in fact, a sub-exponential spectrum is necessary. We conclude that non-stationary states exist even down to the very fine phase bins.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.1
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• pp.43-51
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• 2020

In this study, numerical analysis was carried out on a complex pressure field of blast waves caused by the detonation of high explosives in various environments. The generated blast waves propagated in the air, upon the sudden release of high energy induced by the explosion. Reflected waves were created when the pressure waves encountered certain obstacles such as the ground or the walls of structures. The propagation of the blast waves and its interaction with the reflected waves were simulated. An adaptive mesh refinement was applied to improve the efficiency of distribution of computer resource, for the computational calculation of the blast wave propagation in a wide open space. In addition, the integration of the calculation domains for the explosive and air were considered when the maximum density of the explosive region was below critical value. The results were verified by comparison with the pressure time history from blast wave experiments performed under two topographical conditions.

• Journal of Astronomy and Space Sciences
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• v.29 no.3
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• pp.253-258
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• 2012

We revisit the relation between the peak luminosity $L_{iso}$ and the spectral time lag in the source frame. Since gamma-ray bursts (GRBs) are generally thought to be beamed, it is natural to expect that the collimation-corrected peak luminosity may well correlate with the spectral time lag in the source frame if the lag-luminosity relation in the GRB source frame exists. With 12 long GRBs detected by the Swift satellite, whose redshift and spectral lags in the source frame are known, we computed $L_{0,H}$ and $L_{0,W}$ using bulk Lorentz factors ${\Gamma}_{0,H}$ and ${\Gamma}_{0,W}$ archived in the published literature, where the subscripts H and W represent homogeneous and wind-like circumburst environments, respectively. We have confirmed that the isotropic peak luminosity correlates with the spectral time lag in the source frame. We have also confirmed that there is an anti-correlation between the source-frame spectral lag and the peak energy, $E_{peak}$ (1 + z) in the source frame. We have found that the collimation-corrected luminosity correlates in a similar way with the spectral lag, except that the correlations are somewhat less tight. The correlation in the wind density profile seems to agree with the isotropic peak luminosity case better than in the homogeneous case. Finally we conclude by briefly discussing its implications.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.311-317
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• 2008

As outdoor environment become worse due to concentration of population in large cities, the importance of environmental control strategies such as the arrangement of green space or water space and ventilation paths, has been increasingly recognized. However, most of the studies focus on the assessment on outdoor thermal environment, few studies focus on the interrelationship between thermal environment in residential block and human thermal comfort. The aims of this study is to develop the outdoor planning method to reduce the heating/cooling load in an apartment unit or entire block by the sustainable approaches in outdoor environmental design. In this paper, on the basis of the prior studies, the effect of the outdoor thermal environment on human thermal comfort will be analysed.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.232-237
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• 2008

The integration of PV modules into building facades or roof could raise their temperature that results in the reduction of PV system's electrical power generation. Hot air can be extracted from the space between PV modules and building envelope, and used for heating in buildings. The extraction of hot air from the space will enhance the performance of BIPV systems. The solar collector utilizing these two aspects is called PV/T(photovoltaic/thermal) solar collector. This research is about the development of solar roof system with PV/T collector to apply into buildings. A test cell experiment was performed with the PVT roof installed: It found that the hot air supply from the PVT air collector contributed to increase the heating efficiency by 2 times and the electrical efficiency by about 8%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.682-687
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• 2011

Calibration mirror mechanism has been widely used for on-board calibration with black body. The calibration mirror is deployed to reflect the radiation energy from the black body to the image sensor for calibrating the sensor system. After the calibration, the calibration mirror is stowed not to hide a main optical path. It also has a fail-safe function which can stow the mirror by just removing the input power of motor when the calibration mirror is stopped at certain position during the calibration. In the present work, the operation concept, design, torque analysis and functional test results of the calibration mirror mechanism with the aforementioned function have been introduced and investigated.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.1
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• pp.27-38
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• 2017

Packet classification is one of the essential functionalities of Internet routers in providing quality of service. Since the arrival rate of input packets can be tens-of-millions per second, wire-speed packet classification has become one of the most challenging tasks. While traditional packet classification only reports a single matching result, new network applications require multiple matching results. Ternary content-addressable memory (TCAM) has been adopted to solve the multi-match classification problem due to its ability to perform fast parallel matching. However, TCAM has a fundamental issue: high power dissipation. Since TCAM is designed for a single match, the applicability of TCAM to multi-match classification is limited. In this paper, we propose a cost- and energy-efficient multi-match classification architecture that combines TCAM with a tuple space search algorithm. The proposed solution uses two small TCAM modules and requires a single-cycle TCAM lookup, two SRAM accesses, and several Bloom filter query cycles for multi-match classifications.

• Journal of the Korean housing association
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• v.24 no.6
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• pp.189-197
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• 2013

The purpose of the study was to analyze the improvement elements depended on housing quality measurement tool related to mental health. The data for the analysis was collected through questionnaire survey method from November 1, 2012 to January 17, 2013, and the sample consisted of 720 respondents living in single detached houses, multi-families detached houses, apartments, and town houses in 4 cities, Seoul, Busan, Daejeon, and Kwangju. The data were analyzed using descriptive statistics. The results of improvement elements are as follows: 1) Pedestrian-threaten street from cars in physical safety 2) A secluded or dark spot and fear of walking at night in social security, 3) Indoor noise, outdoor noise, and evidence of abandoned trash heap/bottle in neighborhood in health & sanitation, 4) Illegal parking and heating control system in facility convenience, 5) Extra kitchen, number of bathrooms, and community spaces in space convenience, 6) Openness and spaciousness of indoor room, and satisfaction of house and neighborhood in comfort, 7) Management common/sharing space in maintenance, 8) Energy saving facility and environment friendly materials use in sustainability, 9) Burden on housing cost, asset value on house, and school district in economic value, 10) Reflection of residents style, surrounding building's number of layers, and neighborhood appearance of preference in housing environment image.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.67.1-67.1
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• 2016

We examined the relations between CME speed and properties of magnetic helicity in the source region such as helicity injection rate and total unsigned magnetic flux, which reflect the magnetic energy in the active region. For this, we selected 22 CMEs occurred during the increasing phase of solar cycle 24, which shows extremely low activities and classified them into two groups according to evolution pattern of helicity injection rate. We then compared the relations with those from previous study based on the events in solar cycle 23. As the results, we found several properties as follows: (1) Both of CME speed and helicity parameters have very small values since we only considered increasing phase; (2) among 22 CMEs, only 6 events (27%) are classified as group B, which show sign reversal of helicity injection and they follow behind of appearance of group A events. This fact is well coincide with the trend of solar cycle 23 that only group A events was observed in the first 3 years of the period; (3) as the solar activity is increasing, the CME speed and helicity parameters are also increasing. Based on the observations of solar cycle 23, the helicity parameters was still increasing in spite of decreasing solar activity after maximum period.